Civil Engineering Reference
In-Depth Information
conservative for high levels of f
c
and
rst prestressed elements correspond
to hollow core slabs (see square A in Fig.
8.15
). One beam (see dashed line square
in Fig.
8.15
) has a clearly lower value of SM than its analogous beam (see square B
in Fig.
8.15
), this is because the beam has a
˃
c
. The
fl
ange width (b
f
= 260 mm) much lower
than its analogous (b
f
= 400
600 mm). Therefore, RILEM & EHE Codes, which
take into account the contribution of the
-
fl
ange width in beams reinforced with
bers are overestimating the contribution of a
fl
ange which is very small. In beams
with
anges of considerable size (b
f
> 400 mm), MC2010 gives higher SM than the
other two codes (RILEM and EHE), which means that determines a lower shear
theoretical value since it neglects the contribution of
fl
fl
uence of the Amount of Fibers, Kg/m
3
8.5.6 In
fl
Reinforced and prestressed beams with
bers are always safe (SM > 1) for all
Codes, according to this database, when the amount of
bers is greater than
125 kg/m
3
(Fig.
8.17
).
8.5.7 General Behavior of Codes for Beams with Only Fibers
Tables
8.10
and
8.11
show that, for the beams reinforced with
bers, MC2010
presents the greater CoV (%) but, it is the safest Code, with the highest value of 5th
percentile (in reinforced and prestressed beams). Codes are safer for prestressed
beams.
2.50
300
CONSERVATIVE
2.25
250
2.00
200
1.75
1.50
150
1.25
100
1.00
50
0.75
UNCONSERVATIVE
0.50
0
kg/m3 (Reinforced beams)
kg/m3 (Prestressed beams)
SM (EHE-08)
SM (MC2010)
SM (RILEM)
Fig. 8.17
Beams transversally reinforced with bers. SM represented versus kg/m
3
of bers
Search WWH ::
Custom Search